il8 



NATURE 



[September 30, 19 15 



apply, is probably the most perfect of all when 

 realisable. This is to make use of mirror or semi- 

 mirror surfaces which reflect their surroundings 

 and thus automatically imitate them. Such a 

 device would be applicable in any surroundings. 



The chief instance known to the author of the 

 use of this method is afforded by the latest Zep- 

 pelins, which are reported to have a coating of 

 bright aluminium powder, which reflects the sky 

 and makes the vessel very diflTicult to detect at any 

 considerable height. For aircraft flying at a 

 height the problem of concealment is a particularly 

 difficult one, as whatever pigment is adopted the 

 framework is seen silhouetted against the bright 

 sky. It is possible that by making use of reflect- 

 ing surfaces, in addition to the other devices men- 

 tioned, this contrast could be considerably lessened. 

 If to a noiseless engine could be added the quality 

 of practical invisibility, aircraft would become 

 very much more dangerous offensive machines 

 than at present. 



Such problems as those mentioned above seem 

 to deserve careful scientific study. Methods of 

 concealment may do much to save the lives of 

 combatants. Moreover, the utility of all vessels 

 employed for scouting purposes, whether aircraft, 

 motors, or submarines, depends to a great extent 

 on their escaping detection. It is therefore surely 

 well worth while to follow up any train of research 

 which offers any promise of approaching in- 

 visibility in the future. J. S. D. 



PROF. W. H. H. HUDSON. 



WE greatly regret to record the death, on 

 September 21, of Prof. W. H. H. Hudson, 

 at the age of seventy-six years. Born in London, 

 he graduated as Third Wrangler in 186 1. He 

 Was then fellow and lecturer of St. John's Col- 

 lege until 1882, when he was appointed professor 

 of mathematics at King's College, London. 

 There, and also as professor of mathematics at 

 Queen's College, Harley Street, he worked until 

 his retirement about twelve years ago. 



It is as a lecturer, and as a constructive re- 

 former of the teaching of elementary mathematics 

 that Prof. Hudsort's vigorous influence will long 

 be felt. Of his numerous pupils many became 

 teachers, and the improvements in modern 

 methods of teaching must be largely due to his 

 inspiration. He edited Barnard Smith's "Arith- 

 metic," published notes on dynamics, gave various 

 addresses on the teaching of elementary mathe- 

 matics, contributed to the mathematics of meteor- 

 ology with a theory of anemoids, and did much to 

 proftiote order and economy in the study of 

 mathematics by adding to its vocabulary terms 

 now generally found useful. He was an active 

 membfer of the conference which reported to the 

 Ldndon County Council on the teaching of arith- 

 metic ; of the councils of the London Mathematical 

 Society and of the Mathematical Association ; and 

 of the governing body of Newnham College, in 

 the welfare of which (as of the education of women 

 generally)' he was warmly interested. 

 NO. 2396, VOL. 96] 



Prof; Hudson's principles received remarkable 

 vindication in the record of his family. By the 

 tragic death on Snowdon, in 1904, of his only son^ 

 Cambridge lost one of its most brilliant Senior 

 Wranglers, and perhaps the most widely accom- 

 pUshed. The researches of Ronald Hudson in 

 Kummer's "Quartic Surface," pubHshed post- 

 humously, placed him in the front rank of geo- 

 meters. The three surviving daughters of Prof. 

 Hudson have all distinguished themselves as 

 mathematicians. 



Few men intimate with the austerities of the 

 most difficult of subjects can have made a wider 

 circle of personal friends than did Prof. Hudson. 

 He had the gift of humour and sympathy which 

 endeared him to all those he taught. He enjoyed 

 traveland recreation to the end of his days, and 

 within the boundaries of mathematical study he 

 knew how to find both. ^ 



NOTES. 



The Rev. Dr. E. W. Barnes, fellow and tutor of 

 Trinity College, Cambridge, has been appointed to 

 the mastership of the Temple. Dr. Barnes Is in his 

 forty-first year, and had a brilliant career at Cam- 

 bridge. He went up to the University as a scholar 

 of Trinity College, and in 1896 was bracketed second 

 Wrangler. A year later he took a first class in the 

 first division of the Mathematical Tripos, part ii., 

 and was first Smith's prizeman in 1898, besides being 

 president of the Union. He was elected a fellow of 

 his college in the same year, and was an instructor 

 at the Royal Military Academy, Woolwich, in 1898-99. 

 He is the author of various memoirs and papers on 

 Gamma functions, integral functions, linear differ- 

 ence equations, and related mathematical subjects. 



The Victoria Cross is given for conspicuous courage 

 in the face of the enemy : and, if we want a good 

 example of such courage, we have it in the English 

 nurse, at the American Hospital at Neuilly, who in- 

 oculated herself with a pure culture of the bacilli of 

 gas-gangrene, that she might help the discovery of 

 the best treatment of" that disease. We rejoice that 

 she now is out of danger of death. The annals of 

 medicine record many similar instances of self- 

 devotion, and doubtless there are others which have 

 gone unrecorded. They have not always been of use 

 to mankind : John Hunter, for example. Inoculated 

 himself with the virus of one of the venereal diseases, 

 but drew a wrong conclusion from the results of the 

 experiment. The amazing self-experiments with 

 yellow fever, in Camp Lazear, were happily not In 

 vain. The protective treatments against cholera,, 

 plague, and typhoid fever were, of course, well tested 

 by their discoverers on themselves before they wer6^ 

 put to national uses. A good essay Is waiting to be 

 written on the whole subject of self-experimentation. 

 Lord Moulton, In his evidence before the Royal Com- 

 mission on Vivisection, discusses the ethics of it, and 

 he does that very well. But formal ethics scarcely' 

 touch the case ; the self-experimenter, in the presence 

 of the enemy, the germs, the havoc they work on 

 men, women, and children, "sees red," and behaves 



